Attachment Insecurity in Rats Subjected to Maternal Separation and Early Weaning: Sex Differences.

Haiyan Zeng,Haiyun Xu,Qingjun Huang,Zijia Yu

doi:10.3389/fnbeh.2021.637678

Abstract

Attachment insecurity in the forms of attachment anxiety and avoidance is associated with mental disorders in humans. In this research field, rodents, especially mice and rats, are commonly used to study social behaviors and underlying biological mechanisms due to their pronounced sociability. However, quantitative assessment of attachment security/insecurity in rodents has been a major challenge. The present study identified attachment insecurity behaviors in rats subjected to maternal separation (MS) during postnatal days (PD) 2–16 and early weaning (EW) during PD 17–21. This MSEW procedure has been used to mimic early life neglect in humans. After MSEW, rats continued to survive until early adulthood when they were subjected to open-field, social interaction, and elevated-plus maze tests. Compared to CNT rats in either gender, MSEW rats moved longer distances at higher velocities in the open-field. The MSEW rats also showed lower ratios of travel distance at central zone over that on whole arena of the open-field compared to CNT rats. In social interaction test, male CNT rats preferred to investigate an empty cage than females; whereas female CNT rats spent more time with a partner-containing cage as compared to males. This gender-specific difference was reversed in MSEW rats. On elevated-plus maze female CNT rats exhibited more risk-taking behaviors as compared to male counterparts. Moreover, female MSEW rats experienced a greater difficulty in making a decision on whether approaching to or averting from which arms of elevated-plus maze. Taken together, male MSEW rats behaved like attachment anxiety while females’ phenotype is alike to attachment avoidance described in humans. These results shall prompt further application of MSEW rat in abnormal psychology and biological psychiatry research.

Highlights

Attachment refers to a selective and enduring bond between individuals including romantic attachment between adults and infant–caregiver attachment
Two-way ANOVA showed (1) no significant interaction between treatment and time (F(3,159) = 0.558, p = 0.644), (2) a significant effect of measuring time on body weight of rat pups (F(3,159) = 2,813.101, p = 0.000), i.e., the body weight of rat pups increased with age, (3) maternal separation and early weaning (MSEW) showed no effect on weight gain of rat pups (F(1,159) = 0.046, p = 0.831) (Figure 2A)
Similar results were found in female rats, i.e., there was no significant interaction between time and treatment (F(3,159) = 0.939, p = 0.423), the body weight of female pups increased with age (F(3,159) = 2,261.789, p = 0.000), but MSEW had no effect on weight gain (F(1,159) = 0.483, p = 0.488) (Figure 2B)

Summary

Introduction

Attachment refers to a selective and enduring bond between individuals including romantic attachment between adults and infant–caregiver attachment. In the latter scenario, attachment describes a complex and highly specific bond established between an infant and his/her caregiver (Bowlby, 1982). It was reported that individuals reared in institutional settings exhibited deficits in emotion regulation, attachment to primary caregivers, MSEW and Attachment Insecurity and cognitive development (O’Connor et al, 2003; Kreppner et al, 2007; Zeanah et al, 2009; Tottenham et al, 2010). A person tends to have a high level of self-esteem, self-stability and satisfaction as it facilitates emotion regulation and enhances affiliative behaviors between peers (Canterberry and Gillath, 2013). Clinical studies have shown that attachment insecurity is associated with some of mental health problems including depression (Catanzaro and Wei, 2020), anxiety (Bosmans et al, 2020), obsessive-compulsive disorder (Doron et al, 2012), post-traumatic stress disorder (Ein-Dor et al, 2010), suicidal tendencies (Gormley and McNiel, 2010), and eating disorders (Illing et al, 2010)

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Results

Conclusion